Feleke Arega

The Hong Kong West Drainage Tunnel (HKWDT) system consists of 34 stormwater intake structures designed to intercept stormwater runoff in upland catchments. During stormwater events, each of these intake structures intercepts and diverts the upstream supercritical flow into a bottom rack chamber connected to a supercritical vortex drop. Small surfac...

The Tai Hang Tung Storage Scheme (THTSS) is an essential part of the West Kowloon Drainage Improvement Project that aims to solve the flooding problem in Mongkok, a congested and densely populated district of the Hong Kong Special Administration Region of China. The heart of the flood detention scheme is a 100,000-m3 underground storage tank beneat...

With increased recognition of the value of tidal wetlands and their defining hydrology, the need for better understanding of tidal flow and mixing characteristics is vital to any wetland restoration and enhancement projects and studies. A numerical modeling study was carried out to study the mixing and transport processes in the tide dominated West...

A numerical modeling study, using an Eulerian tracer and Lagrangian particle-tracking methods, was carried out to map the age of water and residence-time distribution in the tide-dominated East Scott Creek Estuary, South Carolina. A coupled hydrodynamic, solute-transport, and particle-transport model was developed. The flow and solute-transport mod...

TheTai HangTung Storage Scheme (THTSS) aims to solve the flooding problem in Mongkok - a highly densely populated commercial and industrial district ofWest Kowloon, Hong Kong. For a 50-year design storm, a maximum upstream inflow of Q=110m 3/s must be conveyed within acceptablewater levels. The heart of the flood detention scheme is a 100,000m 3 un...

The tidal exchange through the Scott Creek saltmarsh estuary was measured near Big Bay Creek, in Edisto, South Carolina. The techniques used for data collection stemmed from those recommended in previous studies. A bottom-mounted ADCP was used to sample data for 35 days, from the thalweg. A vessel-mounted ADCP was used for 13- hour durations, repea...

Capping contaminated sediments in waterways is an alternate remediation technique to dredging and is typically much cheaper than dredging. When cap material is placed on top of contaminated sediment, it has both a short-term and long-term hydraulic impact on the underlying sediment. A numerical model of consolidation, based on a nonlinear finite st...

A numerical modeling study was carried out to compute average residence time in a tide-dominated East Scott Creek Estuary, South Carolina. The East Scott Creek estuary is a long system of meandering tidal creeks and salt marsh between Edisto Island and the Edisto Beach barrier island, in South Carolina. A coupled hydrodynamic and solute transport m...

The Scott Creek estuary is a long system of meander tidal creeks and salt marsh between Edisto Island and Edisto Beach, South Carolina. A causeway for South Carolina Highway 174 (Edisto Beach Causeway) divides the estuary into two nearly equal-length basins that drain, east through Jeremy Inlet and west through Big Bay Creek, into the Atlantic Ocea...

The Yuen Long Bypass Floodway (YLBF) was designed to collect flows from the Sham Chung River (SCR) and the San Hui Nullah (SHN) and to serve as a diversion channel of the Yuen Long Main Nullah (YLMN). Under a 200-year return period design condition, the floodway was designed (1) to divert a flow of approximately 38 m(3)/s from the supercritical YLM...

Recreational water quality at beaches in California and elsewhere is often poor near the outlets of rivers, estuaries, and lagoons. This condition has prompted interest in the role of wetlands in modulating surface water concentrations of fecal indicator bacteria (FIB), the basis of water quality standards internationally. A model was developed and...

Diffusional mass transfer of dissolved substances across the sediment-water interface in coastal waters is an important factor for realistic determination of sediment oxygen demand (SOD) and nutrient recycle. The benthic diffusive boundary layer inside a cylindrical chamber commonly deployed for in situ measurements of sediment oxygen demand is stu...

Dispersion in unstratified tidal channels is analogous to dispersion in streams. In a southern California inter-tidal wetland characterized by depths of roughly 1 m, a dye study illustrates non-Gaussian longitudinal mixing characteristics which are predicted using a depth-integrated numerical model that uses physically meaningful mixing parameters....

The tidal wetlands of the Santa Ana River in Orange County, California are a combination of engineered flood control channels and partially restored salt marshes. The tidal channels extend several kilometers inland with depths comparable to the amplitude of the tides which force circulation, roughly one meter. As is typical of tidal wetlands, there...

Tidal wetlands in California are mostly estuarine salt marshes characterized by tidal channels and mudflats that are flooded and drained on a semidiurnal basis. Depths are rarely greater than 2 or 3 m, except where dredging occurs for harbor operations, and lengths from head to mouth are usually in the range of 1-10 km. This paper presents a couple...

Marine fish farming is an important commercial practice in Hong Kong. Marine fish farms located in eutrophic coastal waters often face the threat of severe dissolved oxygen depletion associated with algal blooms and red tides. On the other hand, mariculture activities also contribute to pollution. The sustainable management of mariculture requires...

Since the early 1980s excessive discharges of organic waste into Tolo Harbour have created serious problems through nutrient enrichment. A number of eutrophication related problems have been reported which incurred financial losses of billions of dollars and serious ecological imbalance. This work addresses the development, verification and applica...

Thesis (Ph. D.)--University of Hong Kong, 2001. Includes bibliographical references (leaves 189-193).

The time and spatial variation of water quality in Tolo Harbour, a eutrophic landlocked semi-enclosed bay frequented by algal blooms, is studied using a dynamic eutrophication model. Hourly changes of tide levels and currents are computed by a link-node model assuming M2 tidal forcing. Phytoplankton growth is assumed to be limited by solar radiatio...